The thermal transfer recording medium is used for thermal transfer printers. In general, a thermal transfer recording medium is formed of an ink ribbon called a thermal ribbon. This thermal transfer recording medium is composed of a thermal transfer layer provided on one surface of a substrate layer and a heat-resistant lubricating layer (back coat layer) provided on the other surface thereof. The thermal transfer layer is an ink layer and is transferred to a thermal transfer image receiving sheet by sublimation (sublimation transfer method) or by melting (melt transfer method) of the ink of the thermal transfer layer by application of heat from a thermal head of a printer.
At present, among thermal transfer methods, sublimation transfer easily enables full color printing of various images with an increase in functions of printers. Therefore, sublimation transfer is widely used in digital camera self-prints, cards such as identification cards and the like, outputted materials for amusement, and the like. As applications are diversified, thermal transfer printers tend to be smaller in size, faster in speed, and lower in cost, and there is also a growing demand for durability of the obtained printed matter. For this reason, in recent years, thermal transfer recording media having a plurality of thermal transfer layers, in which a protective layer and the like that impart durability to the printed matter are provided on the same side of the substrate sheet so as not to overlap each other, have become widespread.
In such circumstances, along with the diversification and widespread use of the applications, there has been a demand for printed matter having a matte appearance, as well as printed matter having a glossy appearance, in addition to durability of print matter.
In response to such a demand, PTL 1 proposes a protective layer transfer sheet in which a release layer contains a filler to adjust the gloss level of the printed matter. Further, PTL 2 proposes a protective layer transfer sheet that can stably obtain glossy printed matter and semi-glossy printed matter from the same sheet by using (meth)acrylic resin having an acid value of 5.0 or less for the protective layer. Further, PTL 3 proposes a protective layer transfer sheet which contains cellulose acetate butyrate resin having a molecular weight of 50,000 or more and a glass transition temperature (Tg) of 150° C. or more for the protective layer to thereby impart high plasticizer resistance to printed matter.